mp1522 25v step-up converter in a sot23-5 package mp1522 rev. 2.0 www.monolithicpower.com 1 9/21/2007 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2007 mps. all rights reserved. the future of analog ic technology description the mp1522 is a step up converter that generates up to a 25v output voltage from a 2.7v to 25v input. it uses a current limited variable frequency control algorithm to optimize efficiency and minimize external component size and cost. the internal 0.5 ? n-channel mosfet switch can withstand up to 28v allowing the mp1522 to produce high output voltage with high efficiency. the mp1522 includes input under voltage and over temperature protection. the mp1522 is available in tiny 5-pin sot23 packages. evaluation board reference board number dimensions ev0022 2.2?x x 1.5?y x 0.5?z features ? internal 0.5 ? power switch ? output voltage up to 25v ? up to 90% efficiency ? low 1a shutdown current ? input under voltage protection ? thermal shutdown ? internal current limit ? available in tiny 5-pin sot23 packages applications ? handheld computers, pdas ? cell phones ? digital still and video cameras ? small lcd displays ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application mp1522 bias fb sw gnd en 2 4 3 5 1 off on v out 20v v in 3.3v c2 1nf d1 rb751 efficiency (%) 100 90 80 70 60 50 load current (ma) efficiency vs load current with bias tied to v out 1 100 10 1000 3.3v 5.0v 10v v out = 12v
mp1522 ? 25v step-up converter in a sot23-5 package mp1522 rev. 2.0 www.monolithicpower.com 2 9/21/2007 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2007 mps. all rights reserved. package reference part number* package temperature mp1522et sot23-5 ?20 c to +85 c * for tape & reel, add suffix ?z (eg. mp1522et?z) for rohs compliant packaging, add suffix ?lf (eg. mp1522et?lf?z) absolute maxi mum ratings (1) bias .............................................. ?0.3v to 28v sw ................................................. ?0.5v to 28v all other pins................................... ?0.3v to 6v junction temperature...............................150 c solder temperature..................................260 c storage temperature ................?65c to 150 c recommended operating conditions (2) bias supply voltage ....................... 2.7v to 25v output voltage....................................v in to 25v operating temperature .............?20 c to +85 c thermal resistance (3) ja jc sot23-5 ................................ 220 .... 110.. c/w notes: 1) exceeding these ratings may damage the device. 2) the device is not guaranteed to function outside of its operating conditions. 3) measured on approximately 1? square of 1 oz copper. electrical characteristics v bias = v en = 5.0v, t a = +25 c, unless otherwise noted. parameter symbol condition min typ max units supply current (shutdown) i bias (off) v en = 0v 1 3 a supply current (quiescent) i bias(on) v fb = 1.3v 650 750 a min off time, normal operation t off v fb = 1.23v 300 550 700 ns min off time, start-up (4) t off v fb = 0v 1.6 s undervoltage lockout bias under voltage lockout uvlo v bias rising, 100mv hysteresis (typical) 2.1 2.3 2.65 v enable en threshold v en rising 0.8 1.1 2.0 v en hysteresis 60 mv en input bias current v en = 0v, 5v 1 a feedback comparator fb regulation threshold v fb falling 1.19 1.23 1.27 v fb hysteresis (5) 10 mv fb input bias current v fb = 1.23v ?150 ?80 na output switch sw on-resistance (5) r on v bias = 5.0v 0.5 0.6 ? sw current limit 300 450 ma sw leakage current v sw =25v 10 a thermal shutdown (5) 160 c notes: 4) first 64 pulses after en switches high 5) guaranteed by design. marking top view sw gnd fb 1 2 3 5 4 bias en
mp1522 ? 25v step-up converter in a sot23-5 package mp1522 rev. 2.0 www.monolithicpower.com 3 9/21/2007 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2007 mps. all rights reserved. pin functions pin # name description 1 sw power switch output. sw is the drain of the internal mosfet switch. connect the power inductor and output rectifier to sw . sw can swing between gnd and 25v. 2 gnd ground. 3 fb feedback input. connect a resistive voltage divider from the output voltage to fb to set the output voltage. the feedback regulation threshold is 1.23v. 4 en regulator on/off control input. a high volt age at en turns on the converter, and a low voltage turns it off. when not used, connect en to the input source for automatic startup. if en is driven over 6v, place a 100k ? resistor in series with en. 5 bias internal power input. bias powers the inter nal circuitry. connect bias to the output for enhancement on the internal mosfet gate at low v in . if the input source remains above 3.0v, bias can be connected to the input source to reduce power consumption. operation the mp1522 is a step-up converter that operates from an input voltage as low as 2.7v and generates an output voltage up to 25v. the 0.5 ? internal n-channel mosfet power switch is driven with a variable frequency, constant- peak-current architecture for improved regulation and low operating current. the 550ns minimum off-time is extended to 1.6s during start-up to yield a smooth glitch free turn-on. start-up mode is activated at initial power-up or when exiting the 1a shutdown state. the mp1522 features an internal regulator allowing it to be powered from the output for improved low-input voltage operation, or powered from the input source for reduced power consumption due to quiescent current. control logic off on regulator v in l1 d1 c1 c4 internal power error amp 1.23v 450ma gnd en bias fb sw r2 r1 c2 c3 r3 -- + current -- + v out gnd 4 2 3 1 5 figure 1?functional block diagram
mp1522 ? 25v step-up converter in a sot23-5 package mp1522 rev. 2.0 www.monolithicpower.com 4 9/21/2007 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2007 mps. all rights reserved. variable frequency constant-peak-current operation when the power mosfet is turned on the inductor current increases until the 0.45a current limit is reached. the power mosfet is then turned off for a minimum of 550ns. at the end of this 550ns transition if the feedback pin is still lower than the 1.23v internal reference the power mosfet will again be turned on, otherwise the mp1522 waits until the voltage drops below the threshold before turning on the mosfet again. this process allows for optimal use of the inductor, while minimizing the output ripple and size of the output capacitor and maintaining low operating current. setting the output voltage the output voltage is set by a resistive voltage divider connecting the output voltage to fb. the voltage divider reduces the output voltage down by the ratio: 1 r 2 r 1 r v v fb out + = solving for v out ? ? ? ? ? ? + = 1 r 2 r 1 r v v fb out where v out is the output voltage, and v fb is the 1.23v feedback threshold. substituting the feedback threshold voltage: ? ? ? ? ? ? + = 1 r 2 r 1 r v 23 . 1 v out r1 can range from 10k ? to 200k ? . r2 is determined the equation: ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = 1 v v 1 r 2 r fb out for example for an output voltage of 20v and r1 = 130k ? the formula yields: ? ? ? ? ? ? ? ? ? ? ? ? ? ? = 1 v 23 . 1 20 k 130 2 r r2 = 2m ? the closest standard 1% resistor value. the feedback divider requires a feed-forward capacitor connected in parallel with r2. this capacitor is typically in the range of 1nf-10nf. on/off control the en input is used to turn the converter on and off. a high input at en turns the converter on and a low level turns the converter off. when en is not being used, connect to the input source for automatic startup. for inputs greater than 6v, pull en to v in through a 100k ? resistor. input capacitor to reduce noise, use a low esr/esl type input capacitor. a 1f surface mount ceramic capacitor close to the input supply side of the inductor minimizes emi and ripple current at the input source. see the section on printed circuit board layout for reducing noise and emissions. a bypass capacitor is typically required to prevent noise at the mp1522. this capacitor should also be a low esr/esl type capacitor. place a 0.1f surface mount ceramic capacitor between bias and gnd as close to the mp1522 as possible. output capacitor to minimize output voltage ripple and noise use a low esr/esl type output capacitor. typically a 1f surface mount ceramic capacitor is sufficient. when using aluminum electrolytics, tantalum or aluminum polymer capacitors the esr/esl dominate the output ripple. see the section on printed circuit board layout. inductor the inductor stores energy during the power mosfet switch on-time. this energy is transferred to the output during the switch off- time. select an inductor whose peak-current rating is greater than the 450ma peak current limit of the mp1522. lower value inductors yield higher switching frequencies and thus lower output ripple voltage. however, using too low a value inductor will cause an increase in peak current limit due to the delay of the current-limit comparator. choose an inductor such that the peak current limit is reached in 550ns or longer. the minimum value inductor for this criterion is: () h v 10 31 . 1 l in 6 ? for maximum v in = 3.3v, use an inductor value greater than 4.7h, and for maximum v in = 5v use an inductor value greater than 6.8h.
mp1522 ? 25v step-up converter in a sot23-5 package mp1522 rev. 2.0 www.monolithicpower.com 5 9/21/2007 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2007 mps. all rights reserved. diode the high switching frequencies of the mp1522 require the use of fast recovery or schottky barrier diodes. in low voltage applications schottky barrier diodes are recommended for maximum efficiency. the reverse breakdown voltage should be approximately 1.5x the output voltage. printed circuit board layout the printed circuit board layout is important in order to minimize noise and prevent erratic operation. keep the ground leads short and robust with minimum lead lengths between the input and output capacitors and ground. place the feedback resistive voltage divider as close to fb as possible to prevent switching noise injection into fb. the use of surface mount capacitors with their low esl is required to minimize noise at the mp1522. use separate power and quiet ground planes connected together at a single point whenever possible to minimize . ground . bounce. table 1?output current vs. input voltage v in (v) v out (v) i out (ma) 3.3 5 67 3.3 12 28 3.3 18 15 3.3 25 10 5 12 44 5 18 32 5 25 19 10 12 122 10 18 75 10 25 51 mp1522 bias fb sw gnd en 2 4 3 5 1 off on v out 20v v in 3.3v c2 1nf d1 rb751 figure 2?typical boost application
mp1522 ? 25v step-up converter in a sot23-5 package notice: the information in this document is subject to change wi thout notice. users should warra nt and guarantee that third party intellectual property rights are not infringed upon w hen integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp1522 rev. 2.0 www.monolithicpower.com 6 9/21/2007 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2007 mps. all rights reserved. package information sot23-5 0.30 0.50 seating plane 0.95 bsc 0.90 1.30 1.45 max 0.00 0.15 top view front view side view recommended land pattern 2.80 3.00 1.50 1.70 2.60 3.00 1 3 4 5 0.09 0.20 note: 1) all dimensions are in millimeters. 2) package length does not include mold flash, protrusion or gate burr. 3) package width does not include interlead flash or protrusion. 4) lead coplanarity (bottom of leads after forming) shall be 0.10 millimeters max. 5) drawing conforms to jedec mo-178, variation aa. 6) drawing is not to scale. 0.30 0.55 0 o -8 o 0.25 bsc gauge plane 2.60 typ 1.20 typ 0.95 bsc 0.60 typ see detail "a" detail a
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